Once again, researchers have concluded that moderate alcohol drinking is associated with a reduced risk of heart disease.

Action Points

Explain that moderate alcohol drinking (one or two drinks a day, or between 12.5 and 25 grams of alcohol) is associated with a reduced risk of heart disease.

Note that in one meta-analysis, moderate drinking introduced favorable changes in several biomarkers associated with coronary heart disease risk, and that different types of alcohol -- beer, wine, and spirits -- had similar effects on the biomarkers.

Once again, researchers have concluded that moderate alcohol drinking is associated with a reduced risk of heart disease.

But in two companion meta-analyses published online in BMJ they also argue that evidence is mounting that the association is causal -- that a drink or two a day prevents mortality from cardiovascular disease.

From a public health perspective, the challenge now is to caution against excessive drinking while ensuring that people understand the potential benefits of moderate consumption, according to William Ghali, MD, of the University of Calgary, who with colleagues conducted the research.

Ghali and colleagues noted that the association is not new, but argued that the last major review of the topic took place in 2006 and since more research has appeared in subsequent years a new meta-analysis and systemic review was warranted.

For one study, they searched published literature for prospective cohort studies on the association between alcohol consumption and overall mortality from cardiovascular disease, incidence of and mortality from coronary heart disease, and incidence of and mortality from stroke.

For the other, they searched for studies that compared fasting levels of specific biological markers associated with coronary heart disease after alcohol use with those observed after a period of abstinence.

For the first meta-analysis, they found 84 studies that looked at the outcomes of interest. Pooled adjusted relative risks for alcohol drinkers compared with nondrinkers in random effects models showed alcohol consumption was associated with a reduced risk of:

On the other hand, stroke incidence and mortality were not significantly associated with drinking alcohol, Ghali and colleagues reported.

Analysis of dose-response curves suggested that the lowest risk of coronary heart disease mortality occurred with between one and two drinks a day, defined as between 12.5 and 25 grams of alcohol.

For stroke mortality, the lowest risk occurred at no more than one drink a day, and the risk rose with increasing consumption.

Interestingly, a secondary analysis of all-cause mortality showed a lower risk for drinkers compared with nondrinkers; the relative risk was 0.87 with a 95% confidence interval from 0.83 to 0.92.

In the other study, the researchers performed a meta-analysis on 63 intervention studies that analyzed biomarkers including lipids, inflammatory markers, endothelial cell function markers, and adipocyte hormones. Forty-four had data in formats that permitted pooled analyses.

The researchers found that moderate drinking introduced favorable changes in several biomarkers associated with coronary heart disease risk. Specifically, alcohol:

The different types of alcohol -- beer, wine, and spirits -- had similar effects on the biomarkers, the researchers found, suggesting it's the alcohol itself that is causing the changes, rather than other constituents of the drinks.

The researchers cautioned that the findings are only indirect evidence of a causal role for alcohol in the association with reduced heart risk.

Ghali and colleagues noted that drinking alcohol has other impacts -- such as injury -- and called for robust studies that would evaluate a range of endpoints simultaneously in order to distinguish those who would benefit from alcohol from those who might not.

That said, the available evidence suggests that "moderate alcohol consumption is associated with net benefit, at least in populations similar to those studied in the extant literature," they concluded.

Both studies had support from the Robert Wood Johnson Foundation, the Substance Abuse and Mental Health Services, and the Administration Center for Substance Abuse Treatment.